Watase fumio

ABSTRACT

IN A GROUNDED EMITTER TYPE TRANSISTOR OSCILLATOR WITH ITS OPERATING POINT SET AT A LOW SOURCE VOLTAGE MEANS IS PROVIDED TO DELAY THE SHIFT OF THE OPERATING POINT TOWARD THE SATURATION REGION WHEN THE SOURCE VOLTAGE IS INCREASED RAPIDLY IN A SHORT TIME WHEREBY TO SATISFY THE CONDITION FOR INITIATING OSCILLATIONS.

July 11, 1972 w T s F o Re. 27,428

CRYSTAL-CONTROLLED GROUNDED EMITTBR OSCILLATOR Original Filed Dec. 2'7,1967 FIG.

PRIOR ART FIG. 3

E i 5 J. 2 P 8 5,

collec1or emi'ner volioge (Vc United States Patent 27,428CRYSTAL-CONTROLLED GROUNDED EMITTER OSCILLATOR Fumio Watase, Tokyo,Japan, assignor to Tohoku Oki Electric Company Original No. 3,462,710,dated Aug. 19, 1969, Ser. No.

693,919, Dec. 27, 1967. Application for reissue Jan. 22, 1971, Ser. No.109,066

Claims priority, application Japan, Jan. 12, 1967 (utility model), 42/3,150 I Int. Cl. H0311 /36 U.S. Cl. 331-116 R 3 Claims Matter enclosedin heavy brackets appears in the original patent but forms no part ofthis reissue specification; matter printed in italics indicates theadditions made by reissue.

ABSTRACT OF THE DISCLOSURE In a grounded emitter type transistoroscillator with its operating point set at a low source voltage means isprovided to delay the shift of the operating point toward the saturationregion when the source voltage is increased rapidly in a short timewhereby to satisfy the condition for initiating oscillations.

This invention relates to a grounded emitter type transistor oscillator.

Generally, in a grounded emitter type transistor oscillator with itsoperating point set at a low source voltage, when the source voltage isincreased rapidly in a short time, the oscillation condition of theoscillator is not met whereby it can not oscillate.

Accordingly it is an object of this invention to provide a novelgrounded emitter type transistor oscillator capable of providingpositive oscillations when the operating point thereof is set at a lowsource voltage and when the source voltage is increased rapidly in ashort time.

Another object of this invention is to provide a grounded emitter typetransistor oscillator having simple and inexpensive circuit constructionbut which can oscillate at low source voltages.

These and further objects of this invention can be achieved by providinga grounded emitter type oscillator comprising a transistor, a source, acollector resistor, a base resistor, an emitter resistor and anoscillating element wherein the operating point is set at a low voltage,characterized in that said base resistor is divided into a firstresistor element and a second resistor element, that a capacitor isconnected between the junction of said first and second base resistorelements and the source whereby to delay the base current with respectto the instant of applying the source voltage.

This invention can be more fully understood from the following detaileddescription taken in connection with the accompanying drawing in which:

FIG. 1 shows a connection diagram of a conventional grounded emittertype transistor oscillator;

FIG. 2 shows a connection diagram of one embodiment of the novelgrounded emitter type transistor oscillator and FIG. 3 is a graphshowing operating characteristics of the grounded emitter typeoscillator.

Referring now to FIG. 1 which shows a conventional grounded emitter typetransistor oscillator circuit employing a quartz oscillating element,the collector current and the base current of a transistor T beingsupplied from a source of supply 3, respectively, through a collectorresistor 1 and a base resistor 2. The emitter electrode of thetransistor T is connected to the source via an emitter resistor 4. Aseries circuit including a quartz oscillating ICE element 5 and acapacitor 6 is connected between the collector electrode and the baseelectrode of transistor T,. A capacitor 7 is connected between the baseelectrode of transistor T and one terminal B of the source 3 whilecapacitors 8 and 9 are connected in parallel with collector resistor 1and emitter resistor 4, respectively.

In the oscillating circuit shown in FIG. 1, the operation of which isequivalent to that of a known Colpitts type oscillator, it is nowassumed that resistance values of collector resistor 1, base resistor 2and emitter resistor 4 are denoted by R R and R respectively, and thatthe voltage across the base and emitter electrodes of the transistor isdenoted by V then the collector potential of the transistor T as seenfrom terminal B, or the voltage V of the DC operating point can beexpressed by the following equation:

In the above equation h represents the DC amplification factor oftransistor T and I the collector current. It will be clear that if hwere maintained constant with respect to collector current 1,, K wouldbecome a constant.

FIG. 3 shows the operating characteristics of the oscillator circuitshown in FIG. 1 wherein curve a represents a plot of collector-emittervoltage vs. collector current by taking the base current of thetransistor as the parameter. Curve b represents the DC loadcharacteristics of the collector electrode of the transistor T and thepoint of intersection P between curves a and brepresents the operatingpoint of the oscillator. The locus of the operating point P when thebase current of the transistor T is varied is shown by curve C.Similarly curve d represents the DC load characteristic of the collectorelectrode of the transistor T for the case wherein the source voltage islower than that of the case shown by curve b. The locus of the operatingpoint when it is set at such a low source voltage is shown by curve e.Stated in another way, it may be said that curve e corresponds to thecase wherein the constant K in the above equation is smaller than thatof the case shown by curve c.

In the oscillating circuit shown in FIG. 1, when the circuit isoperating under a low source voltage its set operating point can beobtained on curved shown in FIG. 3 which means that the correspondingconstant K should be small. It is assumed now that the set operatingpoint is denoted by P Under this condition, when the source voltage isgradually increased the condition for initiating oscillation could besatisfied thus providing satisfactory oscillations. If the sourcevoltage of a large magnitude were applied in the form of a pulse (or astep) the operating point P will be quickly moved topoint P thusapproaching the saturation region. In other words, in an oscillationcircuit with the constant K set to a small value, a rapid increase inthe source voltage causes the operating point to approach the saturationregion, which means a relative decrease in the amplification factor oftransistor T included in the oscillation circuit. As a result, itbecomes impossible to satisfy the condition of initiating oscillationsin the oscillation circuit thus disabling the same.

In order to eliminate this difficulty, in accordance with thisinvention, in an oscillation circuit with its operating point set at alow source voltage, there is provided means to delay the shift of theoperating point to the saturating region when the source voltage isquickly increased in a ihOI't time whereby to satisfy the condition forinitiating )scillations.

FIG. 2 illustrates one example of the ground emitter ;ype oscillatorcircuit embodying this invention which is iubstantially identical tothat shown in FIG. 1 except ;hat the base resistor 2, shown in FIG. 1 isdivided into ;wo sections, i.e., resistors 21 and 22 and that acapacitor [1 is connected between the junction between these lividedresistors and terminal B of source 3. With this arrangement, the basecurrent of transistor T will be delayed with respect to the instant ofapplication of the source voltage whereby the interval of time in whichthe operating point reaches the saturation region or the period ofreduced amplification factor can be reduced thus satistying thecondition of initiating oscillations at the time of applying a highsource voltage.

While in the above described embodiment an oscillator utilizing a quartzoscillating element has been described it should be understood that thisinvention is not limited to the utilization of a crystal oscillatingelement but can be equally applied to any other grounded emitter typeascillator utilizing other types of oscillating elements.

What is claimed is:

1. 1n a grounded emitter transistor oscillator including:

a transistor (T having base, emitter and collector electrodes;

a source of voltage (3) having first (A) and second (B) terminals;

a collector resistor (1) coupling said first terminal (A) of said sourceto said collector electrode;

a base resistor (21, 22) coupling said base electrode to said firstterminal (A);

an emitter resistor (4) coupling said emitter electrode to the secondterminal (B) of said source; an oscillating element (5) coupled betweensaid base and collector electrodes; the values of said resistors beingchosen such that the operating point of the oscillator is set at a lowvoltage; the improvement wherein said base resistor is comprised offirst (21) and second (22) series coupled resistors, and a capacitor(11) is coupled between the junction (10) of said first and secondresistors (21 and 22, respectively), and said source (3) to delay thebase current when said source voltage is applied. 2. The oscillator ofclaim 1 wherein said oscillating element (5) is a quartz element.

3. The oscillator of claim 1 wherein said capacitor (11) is coupledbetween said junction (10) and the second terminal (B) of said source(3) References Cited The following references, cited by the Examiner,are of record in the patented file of this patent or the originalpatent.

UNITED STATES PATENTS 3,251,007 5/1966 Schmitt 33l-116R ROY LAKE,Primary Examiner S. H. GRIMM, Assistant Examiner US. Cl. X.R. 331-164-

